Field of the Invention
The invention relates to an adjusting device for a gripper opening cam in a chain delivery of a sheet-fed printing press, wherein grippers disposed on gripper carriages of endlessly revolving chains run with a cam roller onto the gripper opening cam for opening the grippers, including an adjusting shaft rotatably supported in the machine frame and having an axis, a lever arm pivotable about an axis transverse to the adjusting shaft axis and articulatingly connected to the gripper opening cam, and a coupling gear for converting rotation of the adjusting shaft into pivoting of the lever arm.
An adjusting device which has the foregoing general structural features has become known heretofore from the published German Patent Document DE 30 02 591 C2. In this heretofore known arrangement, the gripper opening cam is disposed on the axis of a chain deflector at the rear end of a sheet pile and is adjustable by swiveling about this axis, to permit changes in the instant of gripper opening so as to adapt to different materials to be imprinted and to other operation factors. To that end, the gripper opening cam is connected via a coupler to a lever which is disposed on a shaft journalled in the printing-press frame transversely to a sheet transport direction, and is swivellable about the axis of this shaft by a worm gear transmission. The worm gear transmission has a worm gear which is seated on an adjusting shaft likewise journalled in the press housing and rotatable by a hand wheel or the like. Several revolutions of the hand wheel and of the adjusting shaft, respectively, are required for traversing the entire adjusting angle. From German Patent 20 40 670, it has become known to provide a swivel lever for adjusting the gripper opening cam to accomplish the aforementioned purpose, the swivel lever having a rather long swivel path and, thereby, permitting the gripper opening cam to have a relatively wide adjusting-angle range. Once the position of the gripper opening cam has been adjusted or set, it is fixed by a brake which must be released in order to effect the adjustment.
Also known heretofore are means, which are independent of the adjusting device, for indicating the position of the gripper opening cam.